UN 1805 — Phosphoric acid, solution
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1805 is Phosphoric acid, solution, a Class 8 corrosive acid assigned to ERG Guide 154. It is usually a low-volatility aqueous acid solution, but concentrated material can burn tissue and generate heat when diluted.
Hazard overview: UN 1805 presents corrosive liquid, acid mist, heat-on-dilution and acidic-runoff hazards. Contact with some metals may release flammable hydrogen gas.
Response guidance: For a UN 1805 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 154. Establish incident command, isolate the area, stay upwind, prevent incompatible contact, control runoff and choose entry or fire-control actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1805 should emphasize corrosive exposure routes, water or oxidizer incompatibility where applicable, air monitoring, PPE selection, decontamination and runoff containment. Use ERG 154, SDS and local SOP.
Regulatory context: Phosphoric acid, solution is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by concentration, formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Phosphoric acid, solution should be stored in tightly closed compatible containers in a secure, cool, dry, well-ventilated hazardous-material area according to SDS and local procedures.
UN 1805 Quick Details
Common Hazards of UN 1805
- CORROSIVE acid solution; inhalation, ingestion or skin/eye contact may cause severe injury.
- Mist or concentrated solution can burn eyes, skin and respiratory tissue.
- Dilution with water may generate heat, especially with concentrated solutions.
- Generally non-flammable, but fire may produce irritating phosphorus oxide fumes.
- Runoff may be acidic and corrosive.
- Contact with some metals may release flammable hydrogen gas.
- Containers may rupture or fail when heated.
Chemical Identity & Physical Properties
Clear, colorless to pale yellow viscous liquid. Odorless or has a faint acidic odor. Solution concentration typically ranges from 50-85%.
| Also known as | Orthophosphoric acidH3PO4Phosphoric acid solutionWhite phosphoric acid |
| CAS Number | 7664-38-2 |
| Appearance | Clear, colorless to pale yellow viscous liquid. Odorless or has a faint acidic odor. Solution concentration typically ranges from 50-85%. |
| Flash Point | Not applicable (non-flammable aqueous solution) |
| Boiling Point | 158C (316F) for 85% solution; varies with concentration |
| Vapor Density | Not applicable (low volatility aqueous solution) |
| Water Reactivity | Miscible with water; dilution generates heat but no violent reaction |
Fireground Response Guidance — UN 1805
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, mist, dust, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing selected from SDS for corrosive contact.
Isolation & Evacuation
First Actions for a UN 1805 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing vapors, fumes, dust, mist or spray and avoid skin or eye contact.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if vapor, dust, fire involvement, water reaction or unknown concentration is present.
- Use ERG Guide 154, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1805 — Phosphoric acid, solutionUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.